Rolling mill method and apparatus



Jan. 27, 1970 J. w. O'BRIEN ROLLING MILL memos AND APPARATUS 6 Sheets-Sheet 1 Filed Jan. 25. 1967 INVENTOR. JEfiEM/A/f W. aim/19v 4 7' TOR/VH4 Jan, 2751970 w. O'BRIEN ROLLING MILL METHOD AND APPARATUS 6 Sheets-Sheet 2 Filed Jan. 25., 1 967 ATTORNEK Ja n. 27, I970 J. WuO'BRlEN I 3,

ROLLING MILL METHOD AND APPARATUS Filed Jam 25. 1967 e sheets-sheet 5 Jan. 27, 1970' J. w. O'BRIEN ROLLING MILL METHOD AND APPARATUS 6 Sheets-Sheet 4 Filed Jan. 25, 1967 wk R m m M H W w 5/ Jan. 21, 19.70 w c ;f au-:N 3,491,571 ROLLING m n-gm METHOD AND APPARATUS Filed Jan. 25, 19.67 6 Sheets-Sheet 5 I N VE2 ITOR. 1525/1/44 144 oaz/zw BY /4 fl a;

Jan. 27; 1970 J. W- ,..I OTVBRIEN. 3,491,571

ROLLING mp1. METHOD AND APPARATUS Filed Jax i. 25,1967 v e Sheets-Sheet s United States Patent 3,491,571 ROLLING MILL METHOD AND APPARATUS Jeremiah Wagner OBrien, Pittsburgh, Pa., assignor to United Engineering and Foundry Company, Pittsburgh, Pin, a corporation of Pennsylvania Filed Jan. 25, 1967, Ser. No. 611,692 Claims priority, application Great Britain, Feb. 14, 1966, 6,444/ 66 Int. Cl. B21b 31/30 U.S. Cl. 72244 11 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a method of and apparatus for rolling elongated material, and, more particularly to a method and apparatus for providing a constant roll gap for producing material within extremely close tolerances.

While the present invention may be employed in conjunction with various types of mills, for the purpose of explanation and illustration its utilization in connection with a rod or bar mill has been selected. For such mills it is desirable to employ a mill design that possesses maximum rigidity in order to produce very constant cross sectional products.

Conventional rod and bar mills of modern design employ a standard mill construction, including a pair of relatively long rolls and have formed therein multiple roll grooves, the rolls being supported by neck bearings at each end and mounted in chocks which are contained within a pair of mill housings. Roll adjustment is made by means of a pair of screwdowns or wedges or by both,

and these mills are usually hydraulically balanced to take up most of the mechanical clearances, although not the clearance of the bearings. The housings and roll diameters are relatively large in order to reduce deflections and with respect to the rolls, wear is controlled by moving to a new groove in order to keep the resulting cross section Within commercial tolerances. Recent demands for mills to produce very close tolerance products, for example one-half of standard tolerances, points up the limitation of such mills in not being able to meet these very stiff requirements.

These new requirements create the need for a mill that is (l) extremely rigid to thereby reduce the effect of spring or deflection under the rolling loads that vary with a change in cross section of the entering workpiece and temperature and (2) of a roll material that will greatly reduce the wear of the roll grooves and (3) of smaller roll diameters that will reduce the spreading eifect characteristic of large rolls employed in conventional mills.

Some attempts have been made in this direction, but as yet they have not satisfactorily solved the problem. Today it is possible to obtain roll materials either by hard facing or by using inserts of tungsten carbide that greatly extend the life of the roll groove. This increased groove life combined with a design which makes roll changing relatively easy eliminates the necessity of employing rolls with multiple grooves. This has led to more recent designs employing overhung rolls with only one groove. In cases where multiple strand rolling is desired, these mills are made up of separate groups of tandem arranged finishing stands, one group for each strand, which has the added advantage of better synchronization of the stand and, consequently, more uniform tension between stands. Also this arrangement makes possible roll changes on one finishing group while the others continue to operate.

These newer developed mills employing an overhung roll design also employ smaller diameter rolls than conventional mills and usually contain only one roll groove to cut down the amount of overhang of the roll and, consequently, to retain as much stiffness or rigidity as possible under the prevailing conditions.

Recognizing the problem of stitfness or rigidity in these new overhung type mills where the size of the parts is restricted by the desire to keep the roll diameter small, one design shown in US. Patent No, 3,190,098 which issued to I. Wilson on June 22, 1965, proposes a construction wherein the upper roll is overhung from one side while the cooperating lower roll is overhung from the opposite side, thus allowing the roll supporting shafts to be made larger in diameter than the more usual overhung design where the roll supporting shafts are on the same side. The design of the above patent also includes wedges to take up the mechanical clearances in the housing and chock parts and a third bearing is provided mounted between the two main bearings which is hydraulically loaded to apply an initial load to the bearings and housing. This design recognizes the problem of rigidity and in this respect is an advancement over earlier known commercial designs, Its improvement is mainly in providing a larger mill modulus because of the increased stiffness of the roll supporting shafts. Its third bearing which is hydraulically loaded adds little to rigidity except for the taking up of mechanical clearances because the rolling load adds to the initial hydraulic loading and, consequently, does not add to mill stilfness.

Recognizing the advantages of mills with small overhung rolls, the present invention employs a new and novel construction which results in a very rigid mill resulting in a substantially constant roll gap.

In accordance with the above discussion it is an object of the present invention to provide in a rolling mill the method of and apparatus for producing a substantially constant roll gap, including the means and process of applying a preloading force to the rolls assembly axially of the separating force developed during rolling greater than the rolling force and in a direction so that the rolling force relieves the prestressed preloading force, and wherein the construction is such that the preloading force is automatically decreased by at least a portion of the loading force.

More specifically, the present invention provides a method of rolling elongated material in which the material is fed between two roll assemblies which are rotatably carried in an overhung fashion by a support, subjecting the roll assemblies to a preloading force at a location offset from the separating force created due to rolling, and in a manner that the separating force will cause a lessening of the preloading force, controlling the preloading force to be at least greater than the separating force, and wherein the value of the preloading force is automatically decreased by at least a portion of the separating force.

Another object of the present invention is to provide in a rolling mill for rolling elongated material comprising two roll assemblies which are rotatably carried in an .overhung fashion by a support, means for subjecting the roll assemblies to a preloading force greater than the separating force acting on the roll assemblies due to rolling and relieving the separating force, said preloading means located axially of the separating force, the construction and arrangement being such that the separating force will cause a lessening of the preloading force which will be automatically decreased by an amount substantially equal to any increase in the separating force so as to maintain the sum of the two forces substantially constant.

It is a further object of the present invention to provide in a rolling mill having a cooperative pair of overhung rolls between which material is fed, means for applying a preloading force to the ends of the rolls oliset from the rolling load, said preloading force being applied in a direction to cause the rolls to be urged in the same direction as the force due to the rolling load.

It is a still further object of the present invention to provide in a rolling mill for rolling rods and bars and similar products, a housing, an opening in said housing for receiving a bearing-chock assembly of one .of a pair of shafts, a window in said housing for receiving a bearingchock assembly of the other shaft, said bearing-chock assembly of the latter shaft being slidable 'm said window, said shafts having overhung portions for drivingly supporting cooperative pairs of rolls between which a workpiece is fed for rolling, said rolls including single cooperative rolling grooves, opposed arms carried by said shafts outward of the rolls, force exerting means carried by one arm at one end thereof adapted to engage the opposed other arms so as to force the ends .of the arms apart and at the same time the rolls away from each other, said force exerting means capable of exerting a force greater than a given rolling load, force measuring means arranged between the opposed ends of said arms for measuring the magnitude of the force exerting means, the construction being such that the sum of the preloading and rolling loads is held substantially constant automatically without any n ed for changing the preloa-ding force.

These objects, as well as other novel features and advantages of the invention, will be better appreciated when the following description is read along with the accompanying drawings of which:

FIGURE 1 is a sectional view of a rod or bar mill incorporating the features of the present invention;

FIGURE 2 is an elevational view of the mill shown in FIGURE 1;

FIGURE 3 is a sectional view taken on lines IIIIII of FIGURE 1;

FIGURE 4 is a prospective exploded view of certain elements shown in FIGURES 1, 2, and 3;

FIGURE 5 is an elevational view of a second embodiment of the present invention;

FIGURE 6 is an elevational view of a still further embodiment of the invention;

FIGURE 7 is a partial sectional view of a further embodiment of the present invention; and

FIGURE 8 is a sectional view taken on lines VIIIVIII of FIGURE 7.

With reference to the first four figures, there is illustrate-d a housing 10 comprising essentially a solid structure having in its upper portion a bore 11 and below the bore a rectangular shaped window 12. Into the bore 11 there is rotatably received a shaft 13 having at its far end a roller bearing 14 and on the opposite end a sleeve bearing 15. Outward of the bearing 15 and in an .overhung relationship relative to the housing 10 there is rotatably secured a workpiece reducing'roll 16 in which is formed a single groove 17. Into the window 12 is an elongated chock 18 for receiving a shaft 19, the chock, it will be noted, extending substantially through the entire housing 10. The chock principally takes the form in elevation of a block having on its opposed vertical sides identical tapering portions 20. The choc; 18 supports the shaft 19 by a bearing arrangement similar to that providing for the shaft 13 which also has an overhung shaft portion to which there is secured a workpiece reducing roll 21 and which has formed thereon a groove 22, the grooves 17 and 22 cooperating together to form the roll pass for the rod or bar to be produced.

The chock 18 is adapted to be adjusted both horizontally and vertically relative to the housing 10 so that the roll gap can be changed and the proper alignment of the grooves 17 and 22 assured. This is accomplished by providing for the chock 18 an extension 23 which receives a nut 24, the nut being threadably engaged by a horizontally disposed shaft 25, the one end .of which extcnds through the housing 10 at the front of the mill. The end of the shaft 25 is provided with a head so that upon rotation thereof the nut 24 is advanced, hence, advancing the chock horizontally along the engaging tapered surfaces of a pair of wedge elements 28 which are received in the bottom of the housing 10.

Vertical adjustment of the chock 18 is obtained by providing for horizontal displacement of the wedge elements 28, which are inserted in the window 12 wherein their lower non-tapered surfaces rest on the ledges 29 formed in the window of the housing 10 and their upper tapered surfaces 38 engage complementary tapered surfaces 31 formed on the chock 18. In this arrangement advancement horizontally of the elements 28 causes, through the tapered surfaces, vertical displacement of the chock 18. This advancement is achieved by providing a centrally arranged screw 32 which passes through the chock 18 and into a nut 33 rigidly secured in a cross piece 34, that joins together the wedge elements at their inner ends. Once positioning of the chock 18 is accomplished the clearances are taken up by a pair of opposed wedge locking members 36 and 37. These members engage through tapered surfaces 38 the chock in the same plane but opposite the wedge elements 28 and are provided with opposite directional screws 39 which allow the members to move in opposite axial directions over tapered surfaces 40 formed at the top of the chock 18. The upper surfaces of the elements 28 have non-tapered surfaces which engage similar surfaces formed in the housing 10.

As noted in FIGURE 1 the shafts 13 and 19 are connected together by gears 41 and 42, the upper gear itself being driven by spindles 43 which are connected to a motor, not shown.

Turning now to the mechanism for applying a preloading to the mill in order to carry out the aforesaid objects of the present invention, reference is again made to FIGURES 1 and 2 and to the outboard portions of the shafts 13 and 19. It will be noted that outward of the rolls 16 and 21 the shafts extend away from the housing 10. On these extended portions there is provided identical roller bearings 45 and 46 which rotate relative to the outer portions of the shafts and which are received in bearing support arms 47 and 4. 8 shown best in FIG- URE 2, the arms have flat opposed surfaces between which there is provided a clearance and are adapted to pivot about the shafts 13 and 19.

The preloading of the mill is accomplished by providing in the top arm 47 at the right side viewing FIG- URE 2, a screw 49 having its lower threaded end received in a nut 51 held by the arm 47. The screw is adapted to pass through the clearance between the arms and engage the lower arm 48 for which purpose there is provided a wearplate 52. At the opposite sides of the arms 47 and 48 in the same relative location that the screw 49 has to the vertical axes of the rolls, there is provided as to the upper arm a load cell 53. The load cell has a plunger 54 at its lower side which extends into the gap between the arms and engages a wearplate 55 received in the lower arm opposite the plunger 54. Thus on pressure being applied by the screw 49 the load cell 53 will measure directly the force of the screw.

It should be emphasized that in order to realize the optimum results the design must be such as to allow for an accurate and direct shifting of the preload from the bearings 45 and 46 to the bearings of the shafts 13 and 19 in which connection it is important that the outboard bearing parts be fairly rigid. If for example, a hydraulic cylinder were used to preload the outboard bearings since the cylinder could follow a change in deflection of the rolling loads, it would simply add to the load already applied by the cylinder. There may be occasions when some softness is desirable, in which connection a spring or like means could be provided at the fulcrum point or under the screw 49. It should be noted that the cell could be mounted under the screw or take the form of a strain gauge mounted on the chock 18. The particular cell selected could be one of many types Well known in the trade.

A better appreciation of the novel results of the present invention may be gained by a mathematical analysis. Let it be assumed that in the illustrated mill successively higher loads are applied to the outboard bearings 45 and 46 which loads are measured by the load cell 53 and the corresponding measurements are made at the roll gap and by this method a mill modulus M is established. By relieving the load on the outboard bearings 45 and 46 a second mill modulus M is established by placing a hydraulic jack between the mill rolls and measuring the roll gap. In accordance with one known formula for expressing the relation of the ratio of the rolling load to the modulus of the mill to determine the thickness of the workpieces, if the roll gap is to be held constant then,

as to the first mill modulus P T 5 F and as to the second L T If PM where T is the thickness of the workpiece issuing from the roll gap, t is the roll gap, L is the preload and M is the first mill modulus, P is the pressure corresponding to the rolling loads and M is the second mill modulus. In this case the preload L would be set so that L just declines to zero when the piece enters the mill rolls therefore in equating the above formulae and since from the fixed geometry of the system the relationship between M and M should be constant we can express this relationship as Practically, in order to insure sufificient preload, L would be set somewhat larger than required so that the initial load on the outboard bearings could be expressed as L+AL and in this case AL would be the remaining outboard load after the piece enters the rolls. Consequently, before entry L AL T F -F and after entry P AL vn m and since from above li MD M1 the gap remains constant. The value of AL can be finally adjusted after the piece enters if the preload has been misjudged.

With reference now to the second embodiment of the present invention illustrated in FIGURE 5 all the components of this embodiment are similar to those illustrated in the previous drawings except that the preload mechanism is not arranged outward of the rolls but between the rolls and the housing. In this arrangement the changing of the rolls is simplified over the arrangement in FIGURE 1. It is deemed only necessary with respect to this second embodiment to identify the preloading device with respect to the housing and rolls. Accordingly, attention is directed to the housing 61 which rotatably supanism there is provided on each shaft 62 and 63 a roll' 67 and 68 having grooves 69 and 71 which cooperate to form the groove for the rod or bar to be rolled. The rolls are secured to the ends of the shafts by a washer 72 which is secured to the faces of the rolls by nut 73.

With reference now to the third embodiment which is shown in FIGURE 6 it, too, is similar to the previous embodiments and for which reason it is only deemed necessary to point out the principal areas of distinction. In this arrangement the preload device is located between the two bearings of the rolls. More specifically, there is provided a roll housing 76 for receiving, as in the case of the previous arrangements, shafts 77 and 78, the shafts having overhung portions outward of the housing 76 to which there is secured in overhung fashion rolls 79 and 81 having grooves 82 and 83 which cooperate together to roll a rod or bar fed between. The shafts are rotatably received in the housing 76 by sleeve bearings 84 toward the front of the mill and roller bearings 85 at the rear of the mill.

Between these two bearings there is provided a bearing cartridge 86 into which the rolls extend and which is located in the vicinity of bearings 87 mounted on the shafts 77 and 78. The bearing cartridge 86 at its top is provided with an opening 88 which at its lower end is enlarged for the reception of a stationary nut 89 and a washer type load cell 91. A bolt 92 passes through the cartridge and engages at its lower end the bearing 87 received on the shaft 77. A similar bearing 87 is received by the lower shaft 78 which is also carried by the cartridge 86. This arrangement is such that on applying a force through rotation of the bolt 92 the end of the bolt engaging the bearing 87 causes a deflection of the shaft 77 in the same direction as the separating force. The reaction force of the bolt 92 is taken into the nut 89 and into the load cell 91 hence, into the cartridge 86- itself to tend to move the cartridge relative to the bolt 92. This movement, of course, will apply a similar force on the lower roll 78 causing this roll to be deflected in a direction of the separating force.

With reference to the embodiment illustrated in FIG- URES 7 and 8, this embodiment differs from the form shown in FIGURES 1, 2, and 3 in that in place of the wedge locking members 36 and 37, piston cylinder assemblies are employed. The employment of the piston cylinder assembly presents the additional advantage of allowing the lower roll to be adjusted while the mill is still being operated. As in the earlier drawings, FIGURES 7 and 8 show a housing 93 for receiving rolls 94 and 95, the bearing chock assembly 96 of the lower roll 95 receiving two pairs of piston cylinder assemblies 97 and 98. The pistons, it will be noted, engage the housing 93 and forcibly urge the bearing chock assembly against the pair of wedge elements 99. On rotation of the screws to raise the lower roll 95, the pistons of the piston cylinder assemblies 97 and 98 are forced into their cylinders, whereas the pistons become more extended when the roll is lowered. When the screw 101 is operated, the bearing chock assembly 96 with its piston cylinder assemblies 97 and 98, which still contact the housing, are moved laterally to permit the roll to be axially adjusted. It will be noted that the application of the preloading pressure outwardly of the rolls 94 and 95 tends to displace the rolls relative to each other, wherein the piston cylinder assemblies 97 and 98 will maintain the chocks in forcible contact with the Wedge elements 99, even though there may be a difference in clearance between the upper portion of the bearing chock assembly 96 and adjacent portion of the housing 93.

In either of the three illustrated forms of the present Invention, it will be appreciated that prior to the mill receiving the rod or bar the prestressed mechanisms will be operated to preload the mill to a load approximately equal to the anticipated rolling loads. As a practical matter, this load will be maintained higher than the anticlpated load by a small value. This will impose on the associated elements a predetermined load, which load will be reduced in direct proportion to the experience of the rolling loads. As a consequence, the load on the mill will be maintained substantially constant, and, hence, the elastic stretch substantially constant, yielding a substantially constant roll gap.

It will be appreciated that in operating the mill by malntalning the sum of the preloading force and the separating force substantially constant, the mill is extremely rigid or, what is referred to in the trade as a very hard mill. It is desirable, however, in certain mill operations to employ a relatively flexible or soft mill. In this event a mill incorporating the features of the present invention can be advantageously employed, wherein the structural components and relationship of parts associated with the prestress means, such as the arms and the lever effect will be made to possess a predetermined limberness. While such a construction will lessen the accuracy of the rolled product, the benefit of the prestress mill construction can still be realized.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated and described what I consrder to represent the best embodiment thereof. However, I desire to have it understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In a rolling mill having a housing for supporting a pair of rotatable shafts,

Separate bearings for rotatably supporting said shafts in said housing,

a pair of cooperative reducing rolls carried by said shafts in a cantilever fashion relative to said housing, an additional bearing for each shaft,

means offset from said rolls for rigidly engaging said additional bearings and applying an initial prestress force to said shafts in a direction such that the reduction force developed by said rolls relieves the prestress force,

said force applying means carried by one of said shafts and constructed and arranged to exert a force on each shaft greater than the reduction force,

means for holding said force applying means in a fixed prestressing position relative to one of said shafts, and

said means being characterized by the fact that on the experience of the reduction force said shafts are displaceable away from the force applying means such that the prestress force is lessened by at least a portion of the reduction force.

2. In a rolling mill according to claim 1, wherein said force applying means is arranged to apply its force in the same direction as the reduction force of the rolls.

3. In a rolling mill having a housing, a pair of shafts supported by said housing, an opening in said housing for receiving a bearing chock assembly for one of said shafts,

a window in said housing for receiving a bearing chock assembly for the other shaft,

said bearing chock assembly of the other shaft being slidable in said window,

said shafts having overhung portions for drivenly supporting cooperative pairs of rolls between which a workpiece is fed for rolling,

a first arm carried by one of said shafts of the rolls at a point axially displaced from said rolls, a second arm carried by the other shaft of the rolls at a point axially displaced from said rolls, force exerting means carried by one arm and arranged to engage the other arm so as to force said arms apart and at the same time the rolls away from each other,

means for holding said force applying means in a fixed prestressing position relative to one of said shafts,

said force exerting means capable of exerting a prestress force greater than the rolling load developed by said rolls,

force measuring means arranged between said arms for measuring the magnitude of the force exerting means, the construction being such that on the experience of a rolling load said shafts are displaced away from the force exerting means such that the prestress force is lessened by at least a portion of the rolling load.

4. In a rolling mill according to claim 3, wherein said rolls each include a single cooperative rolling groove.

5. In a rolling mill according to claim 3, wherein said arms are arranged outward of said rolls.

6. In a rolling mill according to claim 3, wherein said bearing chock received in said window assembly is adjustable in a first direction to axially move the roll it supports relative to said other roll, and wherever this bearing chock assembly is adjustable in a second direction to close the gap between said rolls,

said bearing chock assembly having a projection which includes a tapered surface,

a first wedge slidably carried in said housing engageable with the tapered surface,

means for moving said wedge to effect movement of said bearing chock assembly in said second direction, and

means carried by said housing for moving said bearing chock assembly within said housing in said first direction.

7. In a rolling mill according to claim 6, wherein said tapered surface constitutes a lower surface formed on said projection and wherein said projection has an upper surface, i}

said upper surface of said projection having two opposed tapers,

a second movable wedge arranged between said housing and one of said two opposed tapers of said projection,

a third movable wedge arranged between said housing and the other one of said two opposed tapers of said projection, and

means for moving said second and third wedges into and out of engagement with said two opposed tapers.

8. In a rolling mill according to claim 3, wherein said arms are carried by said shafts inwardly of said rolls and between said .rolls and housing.

9. In a rolling mill according to claim 3, wherein said means for applying the prestress force comprises a threaded screw rotatably received in one of said arms at one end thereof,

one end of said screw being arranged so as to engage the other arm,

said force measuring means arranged on the other end of said one arm adapted to engage the other arm,

and means for mounting said arms for rotatable movement about said shafts. 10. In a rolling mill according to claim 1, wherein said means for applying the initial prestress force includes a yoke arranged inside said housing having an opening through which said shafts extend,

bearing assemblies for said shafts mounted in said yoke the bearing assembly of one of said shafts being carried by said yoke and the bearing assembly of the other shaft being discrete from said yoke, and

said means for applying the initial prestress force carried by said yoke and adapted to engage said discrete bearing.

11. In a rolling mill according to claim 6 including:

a piston cylinder assembly arranged between said housing and said bearing chock assembly received in said window,

in a manner to urge said chock assembly against said wedge and away from said housing,

the constitution being such that the piston cylinder assembly does not interfere with the movement of the bearing chock assembly in said two directions.

1 0 References Cited UNITED STATES PATENTS 3,190,098 6/1965 Wilson 72223 3,327,508 6/ 1967 Brown 72-240 FOREIGN PATENTS 875,035 3/ 1953 Germany.

CHARLES W. LANHAM, Primary Examiner 10 B. J. MUSTAIKAS, Assistant Examiner US. Cl. X.R. 72237 

